Grinding-mill for reducing old rubber stock



(No Model.) 2 SheetsSheet 1.

- N. o. MITCHELL. GRINDING MILL FOR REDUCING OLD RUBBER STOGK.

No. 419,464. Patented Jan. 14, 1890.

N. PETERS. Phbio lithnfingller, Washinglum 01c.

(No Model.)

UNITED STATES PATENT. OFFICE.

NATHANIEL C. MITCHELL, OF PHILADELPHIA, PENNSYLVANIA.

GRINDING-MILL FOR REDUCING OLD RUBBER STOCK.

SPECIFICATION forming part of Letters Patent No. 419,464, dated January14, 1890; Application-filed September 20, 1889. Serial No. 324, 7 (NInfidel) To all whom it may concern:

Be it known that I, NATHANIEL G. MITCH- ELL, .a resident ofPhiladelphia,in the county set forth in the following specification.

This invention relates more particularly to a grinding mill or apparatusfor reducing old rubber stock, as boots and shoes, hose, belting, &c.,to fragments or pieces of a size suitable for further treatment torecover the rubber free from all foreign matters. Such mill consists ofa series of rolls, termed crackerrolls. In practice the first pair ofrolls consists of one coarse corrugated roll and one smooth roll, thesecond of one coarse and one fine corrugated roll, and the third of twofine corrugated rolls; but this arrangement, while useful, is notabsolutely essential. The cracker-rolls are about two feet in length. Ithas been found in using them to act upon waste rubber goods that seriousdifficulties are encountered. The rolls should be kept full from end toend; otherwise they are apt to lash and break; but if kept full thestrain upon them is often too great and produces speedy deterioration.subject to unequal wear and are frequently nicked by pieces of metal inthe stock. When one part is worn more than another, the product lacksuniformity and isunsatisfactory,

These difficulties are wholly obviated by the use of guide-blocksdisposed on the feed side of the rolls, and which reduce the acting facethereof to, say, sixteen or eighteen inches. It is easy to keep thislength of face full and prevent breakage,-while the strain resulting isnot injurious. Uniformity of wear is thus insured, and when the portionof the rolls in use becomes worn orapiece is chipped off the rolls arenot thereby rendered useless, but by adjustment of the guide-blocks newacting faces can be brought into operation and the grinding continuedfor a much longer period than was possible heretofore.

The importance of this improvement will Moreover, the rolls are berealized when it is understood that these rolls, which are veryexpensive, must be returned to the factory when worn to be recut, andthat such recutting can only be done three or four times before therolls are rendered unfit for further use.

A conveyer of any suitable description such as a screw-1nay be employedto deliver the partially-reduced stock from one pair of rolls to thenext. After passing the second pair of rolls the stock is fed onto aninclined screen having a mesh of about one-quarter of an inch. As thestock traverses this screen such fragments as are smaller than the meshfall through. This portion of the stock is sufficiently reduced forfurther treatment. That remaining on the screen passes between the thirdpair of rolls, where the reduction is completed, and thence the stockfalls into an elevator-boot and is hoisted to a chute leading to themagnetic separating apparatus described in my application, Serial No.324,5 7 9, filed September 20, 1889. The inclined screen may, ifdesired, be provided with means for oscillating it to render the removalof the small fragments more certain.

In the accompanying drawings, which form part of this specification,Figure I is a plan view illustrating the arrangement of the severalrolls and accessory devices constituting the mill. Fig. II is a View invertical longitudinal section, illustrating the shakingscreen and thesecond and third pair of roll Figs. III and IV are views in verticalcross-section and front elevation, respectively, illustrating the thirdpair of rolls provided with an oscillatory screen.

Referring more particularly to Figs. I and II, the three sets of rolls(marked, respectively, 1, 2, and '3) are arranged in any convenientrelation, as shown in Fig. I. Set N0. 1 has a smooth roll a and acoarsely-corrugated roll a. No. 2 has a roll I) with fine corrugations,and another I) with coarse corrugations, and No. 3 has two rolls 0 0,both with fine corrugations. The rolls are supported in bearings insuitable supportingframes A and provided with driving-gears 0,

the journal-boxes of one of each pair of rolls being provided withset-screws B, as usual, for regulating the space between the rolls.

Upon the top of side frames A of each pair of rolls are boltedangle-plates d, which support the two guide-rods e, extending parallelwith the axis of the rolls and from end to end thereof. Rods 6 passthrough and support the guide-blocks E, which can be moved lengthwise ofsaid rods to any position. Beds 2 are screw-threaded, and a j am-nut fis placed on each side of each block E to hold it in place. The shape ofblocks E is clearly shown in Figs. II and III.

In practice blocks E are set about sixteen or eighteen inches apart andthe rubber stock is fed in between them. Adjustment of blocks E, whendesired, can be very quickly eifected. One of the blocks E may beremoved altogether and the other set near the middle, so as to utilizeonly the portion of the rolls between it and one of the side frames A.The construction and arrangement of the guide-blocks are the same forall the rolls. The stock, after being partially reduced by the rolls ofmill No. 1, is delivered by hand or by any suitable mechanical applianceto No. 2 for further reduction. The result of the action of these twopairs of rolls is that part of the stock is already in fragmentssufiiciently small for the further operations for recovering therubber,whereas part of it requires still further reduction, which iseffected by mill No. 3. After passing between rolls 1) b of No. 2 thestock slides down an inclined guide G, Fig. II, to the lower end of ascrew conveyer H, by which it is raised and fed onto the upper end of aninclined screen I, which leads to the rolls 0 c of No. 3. Any suitablemechanical lifter would be the equivalent of the conveyer H, and it mayeven be omitted altogether and the stock thrown onto the screen I byhand without departing from the spirit of the invention. As the stockslides by gravity down screen I the smaller fragments pass through itand fall upon an inclined guideway K, which delivers it under roll 0directly to the elevatorboot L. A guard or deflector i is placed underthe screen I to prevent the fragments passing through the latter frombeing caught by roll 0'. The larger pieces of the stock are delivered byscreen I between rolls 0 c, and after being further reduced by theserolls they fall upon guideway K and are conveyed to the elevator-boot L.

Screen I is provided with guide-strips 70, to convey the stock betweenblocks E. These strips are pivoted at Z to the upper end of the frame ofscreen I, so that when the position of blocks E is changed the stripscan also be adjusted properly.

Screen I in Figs. I and II is stationary. As shown in Figs. III and IV,it is arranged to oscillate transversely. The screen at its upper endrests upon a cross-piece m and at its lower end has a tongue at, whichis mortised in a groove in the stationary strip 0,

which forms a continuation of the screen. To one side of thescreen-frame is bolted an arm 13, which carries two smallfriction-rollers q. Between these rollers is a star-shaped cam 'r on ashaft .9, to which motion is communicated through a pulley it. By meansof cam r a rapid oscillatory motion is communicated to screen 1, wherebythe operation of sifting out the smaller fragments of the stock isperformed more effectually.

Any suitable mechanism for shaking screen I may be substituted for thatshown, and other details of construction maybe modified withoutdeparting from the spirit of the invention. It is obvious, moreover,that some of the improvements described may, if desired, be used withoutemploying the others.

Having now fully described my said invention and the manner in which thesame is or may be carried into eflfect, what I claim is-- 1. In a millfor reducing old rubber stock, the combination, with a pair ofcracker-rolls, ofa guide-block E on the feed side of the rolls arrangedto confine the acting surface of the rolls to the portion on one side ofsaid block and to cut oif the portion on the other side thereof,substantially as described.

2. In a mill for reducing old rubber stock, the combination, with a pairof cracker-rolls, of a guide block or blocks E, arranged to confine theacting surface of the rolls to the por' tion on one side of said blockor blocks, and means, as specified, for adjusting said block or blockslengthwise of the rolls, substantially as described.

3. The combination, with a pair of crackerrolls, of an inclined screenleading to the feed side of said rolls, and a guideway for conveying thefragments which pass through said screen under the rolls to the delivery side thereof, substantially as described.

4. The combination, with the cracker-rolls, of an inclined screen forconveying thereto the larger fragments of stock requiring furtherreduction, an inclined guideway under said screen and extending beneathsaid rolls for bringing together the two portions of the stock separatedby said screen, and the guard or deflector for preventing the smallerfragments from being caught by the rolls, substantially as described.

5. In a rubber-grinding mill, the combination of two pairs ofcracker-rolls, an inclined screen, and a conveyer, the conveyer beingadapted to raise all the product of one of the pairs of rolls to theupper end of the inclined screen, and the latter being adapted todeliver the coarser fragments of stock to the other pair of rolls aftersifting out the finer pieces, substantially as described.

6. The combination,with a pair of crackerrolls and a guide block orblocks for reducing their'acting surfaces, of an inclined screen Intestimony whereof I have signed this leading to said rolls, andadjustable guidespecification in the presence of two subscribstrips fordirecting the stock to the space ing witnesses. bounded by theguide-blocks, substantially 5 as described. p 1 NATHANIEL C. MITCHELL.

7. The combination, with the cracker-rolls and the guide block orblocks, of an inclined Witnesses: screen provided With pivotedguide-strips, PHILIP MAURO, and means for oscillating said screen, subC. W. CROASDILL. [o stantially as described.

